Mercury is challenging to capture and can travel long distances causing severe environmental problems. Various techniques have been developed to capture and remove mercury species in flue gas from coal combustion. The flue gas contains a variety of gaseous components such as SOx, NOx, CO2, O2, HCl, H2O, etc, in addition to mercury. The presence of other gases can interfere with the reaction of an adsorbent with mercury species, and therefore, the adsorbent should possess extremely high selectivity and reactivity for mercury. One such absorbent is selenium or nanoselenium due to very strong mercury-selenium bonding.
The optimal operating temperature range for nanoselenium, both in nanoparticle and nanowire forms, is much lower than the typical flue gas treatment temperature of greater than 200° C.). Therefore, during the delivery stage to the Hg capturing site, the nanoselenium adsorbent inevitably experiences high temperatures. The structural integrity of nanoselenium, therefore, cannot be maintained at high temperatures due to the melting point of bulk selenium, which is 217° C. For nanoselenium the melting temperature is even lower. Therefore, at the temperatures at which nanoselenium would be exposed to mercury, there would be decreased surface area due to the melting of the nanoselenium. The decrease in surface area leads to decreased ability to capture and remove mercury. Although the temperature could be decreased to avoid the melting of the nanoselenium, a lower temperature would lead to less mercury being captured because at lower temperatures the absorbent is not as reactive.
Therefore, there is a need to develop a composition that can bind to and remove mercury from a sample at high temperatures without the limitations described above. Additionally, there is a need for a composition that can bind and remove mercury from a sample that can maintain its structural integrity while capturing and removing the mercury and that the integrity is maintained at high temperatures.